This assay is performed using the Chromogenix COATEST activated protein C (APC) resistance V Kit on the ACL TOP instrument. The method uses a modified activated partial thromboplastin time (APTT) test to detect APC resistance. The plasma specimen is prediluted in factor V-deficient plasma. Then the APTT test is performed by incubating patient plasma with a standardized amount of platelet-like phospholipids and activator of the contact factors of the intrinsic coagulation pathway, followed by recalcification of plasma and measurement of clotting time.